As we advanced up the river which winds beneath the GoldenCliffs out of the bowels of the Mountains of Otz to mingle its darkwaters with the grim and mysterious Iss the faint glow which hadappeared before us grew gradually into an all-enveloping radiance.

The river widened until it presented the aspect of a largelake whose vaulted dome, lighted by glowing phosphorescent rock,was splashed with the vivid rays of the diamond, the sapphire,the ruby, and the countless, nameless jewels of Barsoom which layincrusted in the virgin gold which forms the major portion of thesemagnificent cliffs.

Beyond the lighted chamber of the lake was darkness--what laybehind the darkness I could not even guess.

To have followed the thern boat across the gleaming waterwould have been to invite instant detection, and so, though I wasloath to permit Thurid to pass even for an instant beyond my sight,I was forced to wait in the shadows until the other boat had passedfrom my sight at the far extremity of the lake.

Then I paddled out upon the brilliant surface in the directionthey had taken.

When, after what seemed an eternity, I reached the shadows atthe upper end of the lake I found that the river issued from a lowaperture, to pass beneath which it was necessary that I compelWoola to lie flat in the boat, and I, myself, must need bend doublebefore the low roof cleared my head.

Immediately the roof rose again upon the other side, but no longerwas the way brilliantly lighted. Instead only a feeble glow emanatedfrom small and scattered patches of phosphorescent rock in wall and roof.

Directly before me the river ran into this smaller chamber throughthree separate arched openings.

Thurid and the therns were nowhere to be seen--into which ofthe dark holes had they disappeared? There was no means by whichI might know, and so I chose the center opening as being aslikely to lead me in the right direction as another.

Here the way was through utter darkness. The stream was narrow--so narrow that in the blackness I was constantly bumping firstone rock wall and then another as the river wound hither andthither along its flinty bed.

Far ahead I presently heard a deep and sullen roar whichincreased in volume as I advanced, and then broke upon my ears withall the intensity of its mad fury as I swung round a sharp curveinto a dimly lighted stretch of water.

Directly before me the river thundered down from above in amighty waterfall that filled the narrow gorge from side to side,rising far above me several hundred feet--as magnificent aspectacle as I ever had seen.

But the roar--the awful, deafening roar of those tumblingwaters penned in the rocky, subterranean vault! Had the fall notentirely blocked my further passage and shown me that I hadfollowed the wrong course I believe that I should have fled anywaybefore the maddening tumult.

Thurid and the therns could not have come this way. Bystumbling upon the wrong course I had lost the trail, and they hadgained so much ahead of me that now I might not be able to findthem before it was too late, if, in fact, I could find them at all.

It had taken several hours to force my way up to the fallsagainst the strong current, and other hours would be required forthe descent, although the pace would be much swifter.

With a sigh I turned the prow of my craft down stream, andwith mighty strokes hastened with reckless speed through the darkand tortuous channel until once again I came to the chamber intowhich flowed the three branches of the river.

Two unexplored channels still remained from which to choose;nor was there any means by which I could judge which was the morelikely to lead me to the plotters.

Never in my life, that I can recall, have I suffered such anagony of indecision. So much depended upon a correct choice;so much depended upon haste.

The hours that I had already lost might seal the fate of theincomparable Dejah Thoris were she not already dead--to sacrificeother hours, and maybe days in a fruitless exploration of anotherblind lead would unquestionably prove fatal.

Several times I essayed the right-hand entrance only to turnback as though warned by some strange intuitive sense thatthis was not the way. At last, convinced by the oft-recurringphenomenon, I cast my all upon the left-hand archway; yet it waswith a lingering doubt that I turned a parting look at the sullenwaters which rolled, dark and forbidding, from beneath the grim,low archway on the right.

And as I looked there came bobbing out upon the current fromthe Stygian darkness of the interior the shell of one of the great,succulent fruits of the sorapus tree.

I could scarce restrain a shout of elation as this silent, insensatemessenger floated past me, on toward the Iss and Korus, for ittold me that journeying Martians were above me on that very stream.

They had eaten of this marvelous fruit which nature concentrateswithin the hard shell of the sorapus nut, and having eaten hadcast the husk overboard. It could have come from no others thanthe party I sought.

Quickly I abandoned all thought of the left-hand passage, anda moment later had turned into the right. The stream soon widened,and recurring areas of phosphorescent rock lighted my way.

I made good time, but was convinced that I was nearly a daybehind those I was tracking. Neither Woola nor I had eaten sincethe previous day, but in so far as he was concerned it mattered butlittle, since practically all the animals of the dead sea bottomsof Mars are able to go for incredible periods without nourishment.

Nor did I suffer. The water of the river was sweet and cold,for it was unpolluted by decaying bodies--like the Iss--and as forfood, why the mere thought that I was nearing my beloved princessraised me above every material want.

As I proceeded, the river became narrower and the currentswift and turbulent--so swift in fact that it was with difficultythat I forced my craft upward at all. I could not have been makingto exceed a hundred yards an hour when, at a bend, I was confrontedby a series of rapids through which the river foamed and boiled ata terrific rate.

My heart sank within me. The sorapus nutshell had proved afalse prophet, and, after all, my intuition had been correct--itwas the left-hand channel that I should have followed.

Had I been a woman I should have wept. At my right was a great,slow-moving eddy that circled far beneath the cliff's overhanging side,and to rest my tired muscles before turning back I let my boat driftinto its embrace.

I was almost prostrated by disappointment. It would meananother half-day's loss of time to retrace my way and take the onlypassage that yet remained unexplored. What hellish fate had led meto select from three possible avenues the two that were wrong?

As the lazy current of the eddy carried me slowly about theperiphery of the watery circle my boat twice touched the rocky sideof the river in the dark recess beneath the cliff. A third time itstruck, gently as it had before, but the contact resulted in adifferent sound--the sound of wood scraping upon wood.

In an instant I was on the alert, for there could be no woodwithin that buried river that had not been man brought. Almostcoincidentally with my first apprehension of the noise, my handshot out across the boat's side, and a second later I felt myfingers gripping the gunwale of another craft.

As though turned to stone I sat in tense and rigid silence,straining my eyes into the utter darkness before me in an effort todiscover if the boat were occupied.

It was entirely possible that there might be men on board itwho were still ignorant of my presence, for the boat was scrapinggently against the rocks upon one side, so that the gentle touch ofmy boat upon the other easily could have gone unnoticed.

Peer as I would I could not penetrate the darkness, and thenI listened intently for the sound of breathing near me; but exceptfor the noise of the rapids, the soft scraping of the boats, andthe lapping of the water at their sides I could distinguish nosound. As usual, I thought rapidly.

A rope lay coiled in the bottom of my own craft. Very softlyI gathered it up, and making one end fast to the bronze ring in theprow I stepped gingerly into the boat beside me. In one hand Igrasped the rope, in the other my keen long-sword.

For a full minute, perhaps, I stood motionless after enteringthe strange craft. It had rocked a trifle beneath my weight, butit had been the scraping of its side against the side of my ownboat that had seemed most likely to alarm its occupants, if therewere any.

But there was no answering sound, and a moment later I hadfelt from stem to stern and found the boat deserted.

Groping with my hands along the face of the rocks to which thecraft was moored, I discovered a narrow ledge which I knew must bethe avenue taken by those who had come before me. That they couldbe none other than Thurid and his party I was convinced by the sizeand build of the boat I had found.

Calling to Woola to follow me I stepped out upon the ledge.The great, savage brute, agile as a cat, crept after me.

As he passed through the boat that had been occupied by Thuridand the therns he emitted a single low growl, and when he camebeside me upon the ledge and my hand rested upon his neck I felthis short mane bristling with anger. I think he sensedtelepathically the recent presence of an enemy, for I had made noeffort to impart to him the nature of our quest or the status ofthose we tracked.

This omission I now made haste to correct, and, after themanner of green Martians with their beasts, I let him knowpartially by the weird and uncanny telepathy of Barsoom and partlyby word of mouth that we were upon the trail of those who hadrecently occupied the boat through which we had just passed.

A soft purr, like that of a great cat, indicated that Woolaunderstood, and then, with a word to him to follow, I turned to theright along the ledge, but scarcely had I done so than I felt hismighty fangs tugging at my leathern harness.

As I turned to discover the cause of his act he continued to pullme steadily in the opposite direction, nor would he desist until Ihad turned about and indicated that I would follow him voluntarily.

Never had I known him to be in error in a matter of tracking,so it was with a feeling of entire security that I moved cautiouslyin the huge beast's wake. Through Cimmerian darkness he movedalong the narrow ledge beside the boiling rapids.

As we advanced, the way led from beneath the overhangingcliffs out into a dim light, and then it was that I saw that thetrail had been cut from the living rock, and that it ran up alongthe river's side beyond the rapids.

For hours we followed the dark and gloomy river farther andfarther into the bowels of Mars. From the direction anddistance I knew that we must be well beneath the Valley Dor,and possibly beneath the Sea of Omean as well--it could notbe much farther now to the Temple of the Sun.

Even as my mind framed the thought, Woola halted suddenlybefore a narrow, arched doorway in the cliff by the trail's side.Quickly he crouched back away from the entrance, at the same timeturning his eyes toward me.

Words could not have more plainly told me that danger of somesort lay near by, and so I pressed quietly forward to his side,and passing him looked into the aperture at our right.

Before me was a fair-sized chamber that, from its appointments,I knew must have at one time been a guardroom. There were racksfor weapons, and slightly raised platforms for the sleeping silksand furs of the warriors, but now its only occupants were two ofthe therns who had been of the party with Thurid and Matai Shang.

The men were in earnest conversation, and from their tones it wasapparent that they were entirely unaware that they had listeners.

"I tell you," one of them was saying, "I do not trust the black one.There was no necessity for leaving us here to guard the way.Against what, pray, should we guard this long-forgotten,abysmal path? It was but a ruse to divide our numbers.

"He will have Matai Shang leave others elsewhere on somepretext or other, and then at last he will fall upon us with hisconfederates and slay us all."

"I believe you, Lakor," replied the other, "there can never beaught else than deadly hatred between thern and First Born. Andwhat think you of the ridiculous matter of the light? `Let thelight shine with the intensity of three radium units for fiftytals, and for one xat let it shine with the intensity of one radiumunit, and then for twenty-five tals with nine units.' Those werehis very words, and to think that wise old Matai Shang shouldlisten to such foolishness."

"Indeed, it is silly," replied Lakor. "It will open nothingother than the way to a quick death for us all. He had to makesome answer when Matai Shang asked him flatly what he should dowhen he came to the Temple of the Sun, and so he made his answerquickly from his imagination--I would wager a hekkador's diademthat he could not now repeat it himself."

"Let us not remain here longer, Lakor," spoke the other thern."Perchance if we hasten after them we may come in time to rescueMatai Shang, and wreak our own vengeance upon the black dator.What say you?"

"Never in a long life," answered Lakor, "have I disobeyed asingle command of the Father of Therns. I shall stay hereuntil I rot if he does not return to bid me elsewhere."

Lakor's companion shook his head.

"You are my superior," he said; "I cannot do other than yousanction, though I still believe that we are foolish to remain."

I, too, thought that they were foolish to remain, for I sawfrom Woola's actions that the trail led through the room where thetwo therns held guard. I had no reason to harbor any considerablelove for this race of self-deified demons, yet I would have passedthem by were it possible without molesting them.

It was worth trying anyway, for a fight might delay us considerably,or even put an end entirely to my search--better men than I havegone down before fighters of meaner ability than that possessedby the fierce thern warriors.

Signaling Woola to heel I stepped suddenly into the room before thetwo men. At sight of me their long-swords flashed from the harnessat their sides, but I raised my hand in a gesture of restraint.

"I seek Thurid, the black dator," I said. "My quarrel is with him,not with you. Let me pass then in peace, for if I mistake not he isas much your enemy as mine, and you can have no cause to protect him."

They lowered their swords and Lakor spoke.

"I know not whom you may be, with the white skin of a thernand the black hair of a red man; but were it only Thurid whosesafety were at stake you might pass, and welcome, in so far as webe concerned.

"Tell us who you be, and what mission calls you to this unknownworld beneath the Valley Dor, then maybe we can see our way tolet you pass upon the errand which we should like to undertakewould our orders permit."

I was surprised that neither of them had recognized me, for Ithought that I was quite sufficiently well known either bypersonal experience or reputation to every thern upon Barsoom asto make my identity immediately apparent in any part of the planet.In fact, I was the only white man upon Mars whose hair was blackand whose eyes were gray, with the exception of my son, Carthoris.

To reveal my identity might be to precipitate an attack, for everythern upon Barsoom knew that to me they owed the fall of theirage-old spiritual supremacy. On the other hand my reputation as afighting man might be sufficient to pass me by these two were theirlivers not of the right complexion to welcome a battle to the death.

To be quite candid I did not attempt to delude myself with anysuch sophistry, since I knew well that upon war-like Mars thereare few cowards, and that every man, whether prince, priest,or peasant, glories in deadly strife. And so I gripped mylong-sword the tighter as I replied to Lakor.

"I believe that you will see the wisdom of permitting me topass unmolested," I said, "for it would avail you nothing to dieuselessly in the rocky bowels of Barsoom merely to protect ahereditary enemy, such as Thurid, Dator of the First Born.

"That you shall die should you elect to oppose me is evidenced bythe moldering corpses of all the many great Barsoomian warriors whohave gone down beneath this blade--I am John Carter, Prince of Helium."

For a moment that name seemed to paralyze the two men; but onlyfor a moment, and then the younger of them, with a vile nameupon his lips, rushed toward me with ready sword.

He had been standing a little behind his companion, Lakor,during our parley, and now, ere he could engage me, the older mangrasped his harness and drew him back.

"Hold!" commanded Lakor. "There will be plenty of time tofight if we find it wise to fight at all. There be good reasonswhy every thern upon Barsoom should yearn to spill the blood ofthe blasphemer, the sacrilegist; but let us mix wisdom with ourrighteous hate. The Prince of Helium is bound upon an errand whichwe ourselves, but a moment since, were wishing that we might undertake.

"Let him go then and slay the black. When he returns we shallstill be here to bar his way to the outer world, and thus we shallhave rid ourselves of two enemies, nor have incurred thedispleasure of the Father of Therns."

As he spoke I could not but note the crafty glint in his evil eyes,and while I saw the apparent logic of his reasoning I felt,subconsciously perhaps, that his words did but veil some sinisterintent. The other thern turned toward him in evident surprise,but when Lakor had whispered a few brief words into his ear he, too,drew back and nodded acquiescence to his superior's suggestion.

"Proceed, John Carter," said Lakor; "but know that if Thuriddoes not lay you low there will be those awaiting your returnwho will see that you never pass again into the sunlight ofthe upper world. Go!"

During our conversation Woola had been growling and bristlingclose to my side. Occasionally he would look up into my face witha low, pleading whine, as though begging for the word that wouldsend him headlong at the bare throats before him. He, too, sensedthe villainy behind the smooth words.

Beyond the therns several doorways opened off the guardroom,and toward the one upon the extreme right Lakor motioned.

"That way leads to Thurid," he said.

But when I would have called Woola to follow me there thebeast whined and held back, and at last ran quickly to the firstopening at the left, where he stood emitting his coughing bark,as though urging me to follow him upon the right way.

I turned a questioning look upon Lakor.

"The brute is seldom wrong," I said, "and while I do not doubtyour superior knowledge, Thern, I think that I shall do well tolisten to the voice of instinct that is backed by love and loyalty."

As I spoke I smiled grimly that he might know without wordsthat I distrusted him.

"As you will," the fellow replied with a shrug. "In the endit shall be all the same."

I turned and followed Woola into the left-hand passage, andthough my back was toward my enemies, my ears were on the alert;yet I heard no sound of pursuit. The passageway was dimly lightedby occasional radium bulbs, the universal lighting medium of Barsoom.

These same lamps may have been doing continuous duty in thesesubterranean chambers for ages, since they require no attentionand are so compounded that they give off but the minutest oftheir substance in the generation of years of luminosity.

We had proceeded for but a short distance when we commenced to passthe mouths of diverging corridors, but not once did Woola hesitate.It was at the opening to one of these corridors upon my right thatI presently heard a sound that spoke more plainly to John Carter,fighting man, than could the words of my mother tongue--it wasthe clank of metal--the metal of a warrior's harness--and itcame from a little distance up the corridor upon my right.

Woola heard it, too, and like a flash he had wheeled and stoodfacing the threatened danger, his mane all abristle and allhis rows of glistening fangs bared by snarling, backdrawn lips.With a gesture I silenced him, and together we drew aside intoanother corridor a few paces farther on.

Here we waited; nor did we have long to wait, for presently wesaw the shadows of two men fall upon the floor of the main corridorathwart the doorway of our hiding place. Very cautiously they weremoving now--the accidental clank that had alarmed me was not repeated.

Presently they came opposite our station; nor was I surprised tosee that the two were Lakor and his companion of the guardroom.

They walked very softly, and in the right hand of each gleameda keen long-sword. They halted quite close to the entrance ofour retreat, whispering to each other.

"Can it be that we have distanced them already?" said Lakor.

"Either that or the beast has led the man upon a wrong trail,"replied the other, "for the way which we took is by far the shorterto this point--for him who knows it. John Carter would have foundit a short road to death had he taken it as you suggested to him."

"Yes," said Lakor, "no amount of fighting ability would havesaved him from the pivoted flagstone. He surely would havestepped upon it, and by now, if the pit beneath it has a bottom,which Thurid denies, he should have been rapidly approaching it.Curses on that calot of his that warned him toward the safer avenue!"

"There be other dangers ahead of him, though," spoke Lakor'sfellow, "which he may not so easily escape--should he succeedin escaping our two good swords. Consider, for example, whatchance he will have, coming unexpectedly into the chamber of----"

I would have given much to have heard the balance of that conversationthat I might have been warned of the perils that lay ahead,but fate intervened, and just at the very instant of all otherinstants that I would not have elected to do it, I sneezed.